The present invention relates to a clean room and more particularly to a modularly constructed load bearing clean room structure having a negative air pressure plenum above the ceiling of the clean room to improve the efficiency of the clean room.
The need for a controlled, contaminant free work area is well recognized in industry and in particular in the semi-conductor industry. Accordingly, specialized clean rooms have been developed which provide a controlled environment in which precise assembly and manufacturing operations can be performed with minimal contamination by air borne particles. The atmosphere in a clean room is typically purified from particle contaminates by the use of high efficiency particle air (HEPA) filters
In the construction of a clean room it is desirable to provide an air flow system which occupies a minimal amount of space while providing the necessary ventilation functions. It is also desirable that the top of the clean room be a structural deck to serve as a mechanical equipment platform and the walls be strong enough to support the deck. It is also desirable to provide a clean room structure which can be quickly assembled at a user's production facility such that the operation of a production facility is interrupted as little as possible during the construction of a clean room. This is particularly important during an expansion of an existing clean room. In addition, during such an expansion, it is desirable to reduce, as much as possible, the amount of dust or dirt generated during the construction of the clean room addition. It is further desirable to construct a clean room in which dust or other contaminates are prevented from collecting on the clean room ceiling which, over time, can work into the clean room environment.
The clean room is of a modular structure which can be prefabricated off-site and assembled at the production facility of the clean room user. Off-site fabrication of the clean room enables the clean room to be assembled using a minimal amount of time and construction space and creating a minimal amount of dust and dirt. The clean room of the present invention includes wall modules having a four foot width that are assembled in a side by side relationship to construct the sidewall of the clean room. The interior of the wall modules serve as air return ducts for the recirculation of the clean room air. Across the top, or spanning the clean room walls, a support deck is constructed using four foot wide deck panels from which downwardly suspends a clean room ceiling structure. Air conditioning and other HVAC equipment is mounted on the top of the support deck. The space between support deck and the clean room ceiling is in communication with the return air side of the HVAC equipment such that the air pressure in this space is less than the atmospheric pressure creating a negative air pressure plenum above the clean room ceiling. The plenum is in communication with the return air ducts in the sidewall modules to draw air from the return air ducts. Air from the clean room enters into the sidewall modules through vents at the base of the sidewall modules. Conditioned air is then returned from the HVAC system through air ducts to a plurality of HEPA filters in the clean room ceiling which filters the conditioned air immediately prior to the air being blown into the clean room interior.
The negative pressure plenum above the clean room ceiling eliminates the accumulation of dust and dirt above the clean room such that over time, no dust or dirt will collect which can infiltrate the clean room environment. This helps to guarantee that cleanliness specifications will be met over the useful life of the clean room. The use of the sidewall modules as return air ducts reduces the space required for the return air system to a minimum and eliminates exposed sheet metal duct work. All of the wall modules serve as air ducts so that even air circulation in the clean room is provided. The modular construction of the clean room enables the individual wall and deck panels to be prefabricated off-site and merely assembled together to form the clean room using a minimal amount of time and creating a minimum of dust and dirt.
The present invention relates to certain improvements in the clean room structure. The wall modules are constructed from a welded framework using two C-channel galvanized steel studs at each vertical edge of the modules. Additional vertical C channel studs are used inside the perimeter framework depending on strength required. An aluminum or steel lined composite panel is placed on the interior and exterior sides of the studs which serve as the interior and exterior surfaces of the clean room wall. The aluminum or steel is first bonded to the composite panel before the panel is secured to the welded frame work. The space between the panels forms the return air duct in the sidewall modules. The depth of the vertical C channel studs is determined by the amount of air required. The sidewall is assembled by placing the modules together with studs of each module abutting a stud of an adjacent module. Each modular panel is a sealed one piece assembly.
The width of the composite panels is slightly less than the width of the welded framework so as to form a gap between the panels which is filled with a flush fitting trim strip to give a finished appearance to the wall and to protect the panel core. The gap is offset from the center of the joint between modules to enable the trim strip to be secured to one of the two steel studs at each joint rather than be secured into the seam between abutting studs. The offset gap is created by attaching the panels to the studs with one vertical edge of the panel substantially flush with the stud edge and the other vertical edge of the panel recessed from the edge of the stud so as to expose the side surface to the stud.
The lower end of the panels terminate approximately one half inch above the floor so that liquid spilled on the floor will not contact and damage the panel core material. In addition, one panel of the module can terminate at the lower end approximately five inches above the floor to provide access into the module interior for fastening the module to the floor. This space between the panel and floor is filled with a cover board fastened to the studs. A cove base molding is applied to the cover board and the joint between the cover board and panel or the floor material is continuously coved up the walls to a height above the cover board.
Windows are constructed in the modules with two window panes, one pane in each panel. The panes are mounted in frames which are secured to an opening in the panels. The window frames are made of a one-piece aluminum extrusion which is bent with relatively large radius curves to form the window corners. By constructing the window frames of one-piece only one seam is created where the frame ends abut. This reduces the opportunity for contaminates to enter the clean room compared to a window frame of four separate pieces joined at each corner.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.